In wireless communication, devices send and receive messages without being physically coupled. Wireless devices can include portable computers, telephones, location sensors (such as those using GPS), and the like. Portable computers with wireless communication capability can be coupled to a computer network, such as the Internet or the World Wide Web. The IEEE 802.11 standard (including 802.11a, 802.11b, and 802.11g) is one known technique for coupling wireless devices to a computer network. In 802.11, wireless devices seek out and select “access points” (herein sometimes called “AP's”), which are themselves physically coupled, for computer communication, to at least a system coordinator. Each wireless device associates itself with a particular AP, with which it communicates. Each wireless device (which might be moving) determines from time to time if it has good communication with its associated AP, and whether it would have better communication with a different AP. Each AP might be coupled to a single device, a collection of devices, or to a computer network.
In any of these cases, the known art exhibits several problems:
One problem is that handoff (deassociating a wireless device from a 1st AP, and associating that wireless device with a 2nd AP) can take substantial time in relation to the communication. This might constrict the wireless devices and AP's from using their full communication ability. This might also reduce the ability of AP's to provide QoS guarantees that are needed for some uses of wireless devices, such as VoIP and other voice or video applications.
A second problem is that each wireless device chooses the AP it associates with, based only on local state visible to the device. This might create a system of device-to-AP associations that results in sub-optimal usage of the wireless spectrum. This might result in lower performance not only for the wireless device that makes the sub-optimal association decision, but for the network as a whole, since wireless is a shared medium.